Sealed bearing with hydrostatic pressure balancing for core barrels

ABSTRACT

A coring device has an elongated tubular drill receiving a tubular core barrel which is mounted on the drill by a bearing and defines with the drill a drilling-fluid passage. The bearing is enclosed in a fluidtight lubrication compartment that must be protected from the drilling fluid. To this end one axial wall of the compartment is formed as a piston which can be displaced axially by a pressure differential between the lubrication compartment and the drilling-fluid passage to hydrostatically equalize the two pressures and prevent cross leakage.

States @onstantinescu et al.

[54] SEALED BEARING WITH 'HYDRQSTATHC PRESSURE BALANCING FOR COREBARRELS Inventors: Doriii' Constantin escu; Sever Cruceanu; EugenSpataru; Nicoiae Mereanu, all of Bucharest, Romania Assignee:

Cercetari Pentru Utilaj Petrolier, Bucharest, Romania Filed: June 17,1971 Appl. No.; 154,145-

U.S. Cl. ..175/228, 175/239, 175/252 .............E2lb 9/20 Field ofSearch ..175/227, 228, 236, 175/239, 244, 246, 249, 252

[56] References Cited,

UNITED STATESPATENTS 3,241,623 3/1966 Martinei ..17s/239x IPCUPlnstitutul De Proiectari Si [451 May 29,1973

3,487,890 l/l970 Martinsen ..l75/228 X 2,555,580 6/1951 Deely ..175/2282,587,231 2/1952 Schierding. .....l75/227 2,621,897 12/1952 Brown r..l75/246 X 3,363,703 1/1968 Shewmake..; ..l75/252 X PrimaryExaminer-David H. Brown Attorney-Karl F. Ross [57] ABSTRACT A coringdevice has an elongated tubular drill receiving a tubular core barrelwhich is mounted on the drill by a bearing and defines with the drill adrilling-fluid passage. The bearing is enclosed in a fluidtightlubrication compartment that must be protected from the drilling fluid.To this end one axial wall of the compartment is formed as apiston'which can be displaced axially by a pressure differential betweenthe lubrication compartment and the drilling-fluid passage tohydrostatically equalize the two pressures and prevent cross leakage.

8Claims, 1 Drawing Figure PATENTEM 3, 735 826 A ll INVENTORS, 0.CONSTANTINESCU E. SPATARU BY N. MEREANU S. CRUCEAN (Karl x SEALEDBEARING WITH HYDROSTATIC PRESSURE BALANCING FOR CORE BARELS FIELD OF THEINVENTION BACKGROUND OF THE INVENTION A coring device is used to samplerock for any of a multitude of purposes, such as in exploring for oil ortesting for foundations. The drill, which is an upright tube having abit at its lower end, cuts an annular cylindrical hole with the corerising in the core barrel, which is another tube extending coaxiallythrough the drill. Drilling fluid serving to cool the bit and carry offthe chips is pumped down through the annular elongated passage betweenthe two tubes, and rises up around the outside of the drill. The drillis connected to the upper end of the core barrel by means of a bearingusually of the roller or ball type.

This bearing clearly must be lubricated with oil or grease. Itsexposure, therefore, to the drilling fluid (which is often drilling mudand water) creates a great hazard. Should any of this mud get into thebearing it will quickly ruin it and thereby cause the drill and barrelto rotate together, thereby fragmenting and ruining the core as well asdestroying a costly piece of equipment.

It has been the general practice simply to form a lubricationcompartment around the bearing which is very tightly sealed so thatentry of drilling fluid is not possible. If the seal is too tight, itrotationally links the core barrel and drill or else is prone to breakdown and thereby defeats the whole purpose of the bearing. If it is tooloose, however, the constant pressure fluctuations in the drilling mudwill pump some mud across the seal into the lubrication compartment andthereby contaminate the lubricant.

OBJECTS OF THE INVENTION It is therefore an object of the presentinvention to 7 provide an improved coring device.

Another object isthe provision of a coring apparatus whose bearingbetween the core barrel and drill is protected from contamination by thedrilling fluid.

Yet another object is to provide a seal which protects such a bearing ina simple and efficient manner while reducing rotational entrainment ofthe core barrel by the drill to a minimum.

'SUMMARYOIF THE INVENTION The above objects are attained, according tothe present invention, in a coring device wherein the compartmentcontaining the bearing is provided with a movable partition 01' wallseparating it from the drill- -in part, surrounding the stern below thepiston, and

communicates through bores with the region surrounding the bearing. Thispiston is sealed by means of a resilient but highly flexible cuffagainst the stem and by means of a conventional seal ring with the innerwall of the compartment, with a pin being provided in the barrel holderto fix the piston rotationally to this holder.

The bearing, according to another feature of the present invention, is apair of roller bearings axially flanking a radially projecting collar ofthe stem and each having one race on the collar and another race fixedto the barrel holder in order to take up thrust. There is littlepossibility of canting of the barrel in the drill since the two are bothquite long and nested, and the drilling fluid fills the annular gapbetween them.

DESCRIPTION OF THE DRAWING The above and other objects, features andadvantages will become apparent from the following description,reference being made to the drawingv whose sole FIGURE is a longitudinalsection through a coring device according to the present invention.

SPECIFIC DESCRIPTION The coring device includes an outer tubular drill111 threaded at one end onto and end piece 15 adapted to be screwed ontothe drill stem. At its other end, the drill tube 11 is threaded onto acalibrating adaptor l3 onto which is threaded the bit 14 which is formedwith a circular flat face 14a on which axially extending bores Mb open.

Within the drill tube'lll is a core barrel l2 threaded at one end into acase 16 for core retainers 17 and at the other end over one end of acore-barrel holder formed by a pair of threadedly interengaged elements1 and 2. A spindle 18 is threaded at one end into the piece 15 with alock nut 18 holding it in place. This spindle S determines the axialpositioning of the open end of the core barrel 12 relative to the bit114 depending on how far into the endpiece 15 it is screwed. A radiallyprojecting abutment collar 23 integral with the spindle 8 is engaged bya pair of races 9a and lltla of respective thrust ball bearings 9 and M]whose other races 9b and 10b, respectively, bear against the parts 2 andl of the core-barrel holder.

Such a coring device is pushed in the direction shown by arrows A downinto the ground. The bit 14 cuts a circular and annular hole in the rockas drilling fluid is pumped through bores 15a in the socket piece 15whence it flows through the annular space 25 surrounding the centralregion of the spindle 8 and then down through the cylindrically annularpassage 24 between the tubes 11 and 12 and out at the bit face Ma frombores Mb. This drilling mud carries off the chips and cools the bit,with the chips and mud thereafter rising against direction A around thedevice in the bore. As the drill cuts its annular hole, the core risesin the barrel 12 which does not rotate so that the core is not brokenup. Any drilling fluid captured in the barrel 12 by the pistonlilre coreis forced through conduit in which is provided a check valve formed by aball 19 resting on a rubber seat 20 held in place by a snap ring 21 andout through a plurality of downwardly inclined bores 26 into the passage24. When the top of the core comes into engagement against the face 1aof the holder ll, 2 the drill will obviously no longer sink, therebysignaling for withdrawal and removal of the core specimen.

The bearings 9 and 10 are lubricated with heavyweight oil or grease. Tothis end a compartment 27a-f is formed between the two holder sections 1and 2. The

compartment 27af comprises a plurality of generally axially extendingbores 27a interconnecting an annular chamber 27b surrounding the stem 8with a chamber 270 containing the bearings 9 and and the collar 23. Inaddition, a bore 27d extending axially through the end region of thespindle 8 has laterially opening branches 27e one of which opens intothe chamber 27b and two of which open into the chamber 27c at the insideof the bearings 9 and 10. The very end of the spindle 8 is journaled inan axially extending bore lb formed in the element 1 and defines a smallchamber 27finto which opens the bore 27d. A lateral plug 22 on theelement 1 can be unthreaded to allow grease to be injected into thischamber 27f.

One wall of the compartment 27b is formedby an axially displaceablecylindrically annular piston 4 slidably received in the element 2 androtatably fixed by a pin 6 in the element 2 engaging in an axial groovein this piston 4. At its end toward the end piece the piston 4 isprovided with a cuff 7 which has an outer periphery received in anannular groove 7a and which has an inner periphery that grips thespindle 8. A snap ring 5 fitted into the element 2 limits travel of thepiston 4 toward the end piece 15 and a seal ring 3 prevents leakagearound the piston 4. The cuff 7 thus has a lip hearing with lightpressure against the lip of the piston defined by stepping the internalbore of the latter.

As the coring device is used, the pressure of the drilling fluid in thepassage 24, will inevitably fluctuate. In order to prevent the pressuredifferential between the passage 24, 25 and the chamber 27a-f fromforcing some of the drilling mud into the compartment 27a-f, the piston4 will displace itself toward the region of lower pressure, therebyequalizing pressures and making leakage highly improbable, if notimpossible. Since a certain amount of thermal expansion of the lubricantin chamber 27a-f is inevitable, some leakage will occur outwardly, andthe piston 4 will compensate for the reduced volume of lubricant bymoving inwardly. Periodically, for instance, each time the barrel 12 isunscrewed from its holder 1, 2 the cap 23 is removed and the compartment27a-f is filled up again, driving the piston 4 against its stop 5. Inthis manner, drilling mud is not able to get into the bearings 9 and 10,thereby giving the core drill, according to this invention, a very longservice life.

We claim:

1. A coring device comprising:

a rotatable hollow drill carrying on one end a bit;

a core barrel received in said bit and forming therewith an annulardrilling-fluid passage;

a bearing between said barrel and said drill, said barrel beingrotatable on said bearing relative to said drill and bit;

vrest of said compartment.

means forming a fluidtight lubrication compartment around said bearing;and

a partition forming a wall of said compartment between said compartmentand said passage and displaceable to vary the volume of said compartmentfor equalizing fluid pressure between said compartment and said passage,said partition being formed by a slidable piston, said drill having anaxial spindle carrying said bearing, said piston being annular andsurrounding said spindle.

2. The device defined in claim 1 wherein said barrel includes a barrelholder connected via said bearing to said spindle, said holder beingformed with an escape conduit extending between the interior of saidbarrel and said passage for releasing fluid caught by said core in saidbarrel.

3. The device defined in claim 1 wherein said drill has at its other endan end piece, said spindle being threadedly engaged in said end piece.

4. The apparatus defined in claim 1 wherein said barrel has a barrelholder connected via said bearing to said spindle, said spindle beingformed with a radially projecting collar, said bearing including a pairof thrust bearings axially flanking said collar, said drill including atits other end an end piece adapted to be connected to a drill stern andformed with at least one generally axially throughgoing boreconstituting part of said passage, said barrel holder being formed witha throughgoing conduit interconnecting its interior with said passageand being provided with a check valve in said conduit permitting fluidflow only from said interior to said passage, said barrel holder beingformed with an axially extending blind bore receiving one end of saidspindle, the other end of said spindle being threadedly received in saidend piece, said barrel holder further being formed with a radiallydirected closable opening, said spindle being formed with an axial boreopening at one end in said blind bore adjacent said opening and at itsother end into said compartment.

5. The device defined in claim 1, further comprising a sealing cuffhaving an outer periphery engaging said piston and an inner peripheryengaging said shaft, and means for rotationally linking said piston tosaid barrel.

6. The device defined in claim 5 wherein the linking means is a radialpin fixed in said barrel.

7. The device'defined in claim 1 wherein said spindle has a radiallyprojecting collar, said bearing including a pair of thrust bearingsflanking said collar.

8. The device defined in claim 7 wherein said barrel includes a barrelholder, said piston defining with said holder an annular chamberconstituting part of said compartment, said means forming-saidcompartment including a bore interconnecting said chamber and the

1. A coring device comprising: a rotatable hollow drill carrying on oneend a bit; a core barrel received in said bit and forming therewith anannular drilling-fluid passage; a bearing between said barrel and saiddrill, said barrel being rotatable on said bearing relative to saiddrill and bit; means forming a fluidtight lubrication compartment aroundsaid bearing; and a partition forming a wall of said compartment betweensaid compartment and said passage and displaceable to vary the volume ofsaid compartment for equalizing fluid pressure between said compartmentand said passage, said partition being formed by a slidable piston, saiddrill having an axial spindle carrying said bearing, said piston beingannular and surrounding said spindle.
 2. The device defined in claim 1wherein said barrel includes a barrel holder connected via said bearingto said spindle, said holder being formed with an escape conduitextending between the interior of said barrel and said passage forreleasing fluid caught by said core in said barrel.
 3. The devicedefined in claim 1 wherein said drill has at its other end an end piece,said spindle being threadedly engaged in said end piece.
 4. Theapparatus defined in claim 1 wherein said barrel has a barrel holderconnected via said bearing to said spindle, said spindle being formedwith a radially projecting collar, said bearing including a pair ofthrust bearings axially flanking said collar, said drill including atits other end an end piece adapted to be connected to a drill stem andformed with at least one generally axially throughgoing boreconstituting part of said passage, said barrel holder being formed witha throughgoing conduit interconnecting its interior with said passageand being provided with a check valve in said conduit permitting fluidflow only from said interior to said passage, said barrel holder beingformed with an axially extending blind bore receiving one end of saidspindle, the other end of said spindle being threadedly received in saidend piece, said barrel holder further being formed with a radiallydirected closable opening, said spindle being formed with an axial boreopening at one end in said blind bore adjacent said opening and at itsother end into said compartment.
 5. The device defined in claim 1,further comprising a sealing cuff having an outer periphery engagingsaid piston and an inner periphery engaging said shaft, and means forrotationally linking said piston to said barrel.
 6. The device definedin claim 5 wherein the linking means is a radial pin fixed in saidbarrel.
 7. The device defined in claim 1 wherein said spindle has aradially projecting collar, said bearing including a pair of thrustbearings flanking said collar.
 8. The device defined in claim 7 whereinsaid barrel includes a barrel holder, said piston defining with saidholder an annular chamber constituting part of said compartment, saidmeans forming said compartment including a bore interconnecting saidchamber and the rest of said compartment.